Could Israeli beachgoers experience a summer with few jellyfish?
Typically, by this time of year, swarms of jellyfish clutter Israeli beaches, clog the filters of power plants and sting those who dare to enter the water.
“In previous years, we would receive reports already from yachtsmen and trawlers who are in the middle of the sea that the jellyfish are on their way to us,” said Prof. Dror Angel, an applied marine ecologist in the Department of Maritime Civilizations at the University of Haifa, who founded and ran the website “Jellyfish Among the People” (www.meduzot.co.il) where people can register their jellyfish encounters.
However, right now, Israeli beaches are almost entirely free of jellyfish.
“Based on previous years when the jellyfish arrived late, and we had small summer swarms, we may see this phenomenon this year as well,” said Dr. Dor Edelist, a marine ecologist and lecturer in the Department of Maritime Civilizations at the University of Haifa. “That is, we will not have a large and dense swarm [of jellyfish]. We say this cautiously, and of course, the reality can still change, but the estimate is reasonable if you look at the past cases.”
Dr. Gur Mizrahi, a research scientist at the Leon H. Charney School of Marine Sciences at the University of Haifa, has a similar perspective – this time from a bird’s eye view. He identifies swarms of jellyfish with the help of an airplane, then sails to them to study them in depth. He took a flight at the beginning of the week but saw no jellyfish.
“The area we surveyed from the air was extensive,” he said. “We flew 10 kilometers from the shoreline along all the beaches, and no jellyfish swarms were observed. We saw a few jellyfish that may have remained in the area from the winter and spring periods.”
First of all, it’s all an estimate, even though each year, researchers learn more about jellyfish and their patterns. There is still a lot they don’t know.
One possibility is a change in ocean currents, which may have swept the jellyfish to other sea areas. However, the researchers do not recognize reports of jellyfish swarms in other places they likely would have reached due to the current change.
Likewise, the northern current, which could sweep the jellyfish to the shores of Israel and more distant areas, was weak this year.
The central assumption on which all the researchers agree is that climate change caused the seawater to warm more slowly this year, and therefore, the comfortable temperature for the jellyfish polyps ideally to “ripen” was delayed by about two weeks. Thus, Angel and Edelist assumed the jellyfish season would start two weeks late. However, that time has passed, and they still have not arrived.
“We still estimate that the reproduction process of the jellyfish did take place two to three weeks late, but it is possible that when they matured, another factor came into the picture, for example, an animal preyed on the jellyfish,” Angel said. “Of course, other things may have happened because the sea is complex and complicated.”
There were other summers in recent years where there we few jellyfish, too, for example, in 2016, 2018 and 2021.
However, they stress the situation could change quickly.
“There is no doubt that a summer without jellyfish is great news for bathers, but if anyone thinks that this is the ‘end of jellyfish,’ they are wrong,” Angel added. “What happened this year does not say anything about the jellyfish population on the seabed when they are still in the polyp stage. Most likely, the polyp colonies still exist and await the right conditions to hatch and release mature jellyfish into the sea.
“So, according to everything we know now, the jellyfish aren’t going to disappear.”